cgo: suggest disable if no set CGO_ENABLED

[chai2010]

cgo depends GCC, some cgo packages are optional.
normal user do not need install GCC if they do not use cgo package.

[ianlancetaylor]

Comment 1:

The cgo tool is part of the overall Go build system.  Many packages expect it to be
present.  The common case is to have GCC installed.  I think it is reasonable for the
default to be that cgo is enabled.

Status changed to WorkingAsIntended.

[chai2010]

Comment 2:

The common case is to have no GCC installed for all windows users.
Go is not only for Linux user, and for lots of Windows user!
Please don't discriminate windows user!

[ianlancetaylor]

Comment 3:

Fair enough about Windows.  But my other points remain true.